The present invention relates to fuel caps for closing filler necks of vehicle fuel tanks. More particularly, the present invention relates to a fuel cap that includes a controllable pressure-relief valve that permits venting of the tank under normal conditions, and also controls fuel leakage from the cap during a roll-over condition.
Conventional fuel caps for closing the filler neck of vehicle fuel tanks generally include a pressure-vacuum valve located in the cap to control the pressure within the fuel tank. Whenever the pressure within the tank reaches a first, predetermined superatmospheric level, the pressure valve portion of the pressure-vacuum valve automatically opens to prevent excess pressure build up within the tank. Whenever the pressure within the tank drops to a predetermined subatmospheric level, the vacuum valve portion of the pressure-vacuum valve opens to equalize the pressure in the tank.
In addition, conventional fuel caps having pressure-vacuum valves may include a roll-over valve disposed on the fuel tank side of the pressure-vacuum valve to isolate the pressure-vacuum valve from fuel and fuel vapor when the vehicle is rolled to a substantially inverted orientation. By isolating the pressure-vacuum valve from fuel and vapor pressure when the cap is in a substantially inverted orientation, the fluid head created by the fuel and the vapor pressure are not permitted to force the pressure valve open which would cause undesired fuel leakage from the cap in the inverted orientation. By isolating the pressure-vacuum valve from the fuel and fuel vapor, the venting capacity of such a conventional fuel cap is eliminated when in the inverted orientation. Although it is normally desirable to prevent fuel leakage from the cap in this orientation, it is sometimes desirable to permit limited fuel leakage from the cap when in the inverted orientation to prevent excessive pressure buildup within the tank.
To permit some fuel leakage from the cap when in the inverted orientation, some conventional fuel caps have included an additional valve member in the cap which opens when the pressure within the tank reaches a second, superatmospheric level, higher than the first superatmospheric level. In such conventional caps, because the normal pressure-vacuum valve has been isolated from the fuel and fuel vapor, the additional pressure valve for venting the excessive pressure within the tank must be a separate valve from the normal pressure-vacuum valve. One problem with this solution to the venting of excess pressure from the tank is that, because an additional venting valve is required, the cap is more complex and more costly to produce.
One object of the present invention is to provide a vented fuel cap with a pressure valve that vents the tank under normal conditions when the pressure within the tank reaches a first, predetermined superatmospheric level and that prevents fuel leakage from the tank when the cap is in a substantially inverted orientation without the use of a roll-over valve that isolates the pressure valve from the fuel and fuel pressure.
Another object of the present invention is to provide a fuel cap having a pressure valve that permits limited fuel leakage from the cap when the cap is in an inverted orientation to prevent excessive buildup of pressure within the tank without the addition of an additional vapor release valve in the cap.
Yet another object of the present invention is to provide a fuel cap with a pressure valve that is always in fluid communication with the fuel tank, and whose operation is selectively controllable so that venting through the pressure valve is permitted whenever pressure within the tank reaches a first, predetermined superatmospheric level when the cap is in a normal orientation, and which prevents fuel leakage from the cap when the cap is in an inverted orientation, and further permits limited fuel leakage from the cap when excessive pressure exists within the tank when in the inverted orientation.
According to the present invention, a fuel cap for use in a vehicle fuel system filler neck is provided. The fuel cap includes closure means for closing the filler neck and pressure relief means for venting fuel vapor in the filler neck through the closure means. The pressure relief means includes a pressure relief valve that is movable between a filler neck-venting position and a non-venting position. Roll-over control means are provided for selectively utilizing liquid fuel and fuel vapor in the filler neck to exert a closing force on the pressure relief valve so that the pressure relief valve is moved to its non-venting position to block discharge of liquid fuel to the atmosphere through the pressure relief means during vehicle rollover.
One feature of the foregoing structure is that roll-over control means are provided for selectively utilizing fuel and fuel vapor to exert a closing force on the pressure relief valve to position the pressure relief valve in the non-venting position during vehicle roll over. One advantage of this feature is that, by utilizing fuel and fuel vapor to control the pressure relief valve, the necessity of a separate roll-over valve to isolate the pressure relief valve from the fuel and fuel vapor is eliminated.
Another feature of the foregoing structure is that fuel and fuel vapor are utilized to selectively control the position of the pressure relief valve. One advantage of this feature is that the medium that is to be controlled, that is the fuel and fuel vapor, dictates and controls the operation of the pressure relief valve. One advantage of this feature is that a single pressure relief valve can be used to control all of the venting activity of the cap.
In preferred embodiments of the present invention, the roll-over control means cooperates with the pressure relief valve to define venting control chamber means for containing fuel and fuel vapor in a predetermined region to permit the fuel and fuel vapor to exert the closing force on the pressure relief valve.
In other preferred embodiments, the roll-over control means further includes passageway means for establishing communication of fuel and fuel vapor in the filler neck with the venting control chamber means. The roll-over control means also includes valve means in the passageway means for blocking the flow of fuel and fuel vapor through the passageway means until the force exerted by the fuel and fuel vapor in the filler neck upon the valve means exceeds a predetermined threshold force during vehicle rollover or the like.
One feature of the foregoing structure is that the venting control chamber means, the passageway means, and the valve means cooperate to utilize the fuel and fuel vapor to exert a control force on the pressure relief valve to control the positioning of that valve. One advantage of this feature is that the pressure relief valve is always in communication with the fuel or fuel vapor, and is the sole mechanism for controlling venting of the cap.
In other preferred embodiments, the venting control chamber means includes safety valve means for exhausting fuel and fuel vapor in excess of a predetermined maximum pressure from the predetermined region so that fuel and fuel vapor in the predetermined region dissipates to lower the pressure in the region to a magnitude less than a minimum pressure magnitude, thereby permitting the pressure relief valve to move to its venting position.
One feature of the foregoing structure is that safety valve means are provided for dissipating the fuel and fuel vapor in the predetermined region to permit the pressure relief valve to move to its venting position. One advantage of this feature is that, should the pressure due to fuel and fuel vapor in the tank exceed a predetermined maximum pressure, the safety valve means functions to dissipate a portion of the fuel and fuel vapor in the predetermined region which is acting to position the pressure relief valve in its non-venting position. By dissipating a portion of this positioning pressure, the pressure relief valve is permitted to move to its venting position to enable a portion of the pressure within the tank to vent to the atmosphere.
Thus, the fuel cap of the present invention is able to control the venting from the cap under normal conditions, and under abnormal conditions such as vehicle roll over. The pressure relief valve in the cap is controlled by a venting control chamber which is in fluid communication with fuel and fuel vapor in the filler neck. The fuel and fuel vapor in the venting control chamber acts to position the pressure relief valve in its non-venting position when the cap is in an inverted orientation and when the combined fluid head created by the fuel in the tank and the fuel vapor is less than a predetermined maximum pressure. When the combined fuel head and fuel vapor pressure exceed this predetermined maximum pressure with the cap in an inverted orientation, the safety valve means acts to dissipate the pressure within the venting control chamber which permits the pressure relief valve to move to its venting position. By permitting the pressure relief valve to move to its venting position under these conditions, the excessive pressure within the tank is enabled to vent to the atmosphere.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.